In various signal processing applications, it is often desirable to modify certain characteristics of a received signal. Such characteristics may include the signal's time base, amplitude, frequency content, repetition rate, and the like. The art is replete with equipments capable of performing such modifications when a signal exhibits low bandwidth, low frequency characteristics. When however, wide bandwidth, high frequency signals are encountered, such equipment is not economically available. For instance, pulse signals in the X-band range, (e.g., approximately 10+ GigaHertz) are often encountered with 0.5 Gigahertz sidebands. Conventional circuits are not available, at reasonable expense, to modify the aforementioned characteristics of such signals.
The prior art discloses various electro-optic systems for processing high frequency signals. D. H. Pritchard in an article entitled "A Reflex Electro-Optic Light Valve Television Display" which appeared in the RCA Review, December 1969 at pages 567-692, describes a television system wherein a cathode ray tube has its mask and face plate replaced by an electro-optic crystal element on which is mounted a segmented mirror. As the tube's electron beam scans over the segmented mirror, charge is deposited on the various segments of the mirror in proportion to the beam's intensity. The front of the electro-optic crystal element is illuminated by a non-coherent light source which has been polarized in one direction. The crystal element modifies the polarization of the reflected light in accordance with the charge appearing on each of the various mirror segments. The beam, as thus modified, is passed through an analyzer and then projected onto a screen for viewing.
Another prior art system which employs an electro-optic crystal for signal processing is described in "Dielectric Optical Properties of Electron-Beam Addressed KD.sub.2 PO.sub.4 ", Casasent et al, Journal of the Optical Society of America, Vol. 64, No. 12, Dec. 19, 1974, pages 1575-1581. The system described therein employs an electron-beam addressed KDP light valve wherein writing is accomplished via an electron gun on the target crystal. Read out occurs as the result of the crystal's modulation of light transmitted therethrough.
A further electro-optic light modulator is described by Schwartz et al in "Electron-Beam-Addressed Microchannel Spatial Light Modulator" appearing in "Optical Engineering, January/February 1985, VOl. 24, No. 1 at pages 119-123. In each of the aforementioned systems, the characteristics of an electro-optic crystal are employed to convert an electrical signal to an optical signal; however, there is no indication of any intention to modify or change the characteristics of the signal, but merely to faithfully reproduce it optically.
Accordingly, it is an object of this invention to employ an electro-optic system to enable modification of a received high frequency signal.
It is a further object of this invention to utilize an electro-optic system to segment an incoming signal so that its various portions can be independently operated upon.